The reaction: The President, Mrs McAleese, and the Taoiseach, Mr Ahern, were among those who extended their sympathies to the relatives of the five people killed in the Wellington Quay bus tragedy in Dublin on Saturday.
There were also calls from Opposition parties for improvements in traffic management in Dublin city centre to prevent a similar tragedy happening again.
Mrs McAleese said: "My thoughts and prayers are with the families of those who have been so tragically killed in Dublin and with those who have been injured in this dreadful event in the midst of our capital."
Mr Ahern, who visited the crash scene on Saturday, said he wished to extend his sincerest sympathies to the families of the dead "at this time of terrible loss.
"It was with great distress that I learned about those who had lost their lives and the many others who have been injured going about their daily lives in Dublin city centre.
"Our thoughts are with the injured and their families. Our prayers are for a swift recovery for those who have been injured. I also wish to extend my thanks to the emergency services who all too often have to deal with tragedy of this kind."
Fine Gael's transport spokesman, Mr Denis Naughten, said he would raise the tragedy with the Minister for Transport, Mr Brennan, in the Dáil.
"This is an awful tragedy for the families involved and I would like to extend sympathy to them on behalf of Fine Gael."
He said Mr Brennan should fully explain the nature of the investigations into the tragedy and circumstances surrounding it.
The Minister should also establish "what information, if any, was provided to the management of Dublin Bus concerning the safety of this particular bus stop, which could have averted the incident or at least reduced the level of fatalities".
Labour's spokesperson on transport, Ms Róisín Shortall, said: "It is absolutely shocking that five people about their normal business on a Saturday afternoon could lose their lives in this way.
"The accident is all the more shocking given that buses are normally a very safe and reliable means of public transport."
"Clearly there must, in due course, be a full investigation into the causes of the accident and procedures put in place to prevent a similar tragedy ever happening again. In the meantime our thoughts must be with all those who were injured and lost their lives."
The leader of the Green Party, Mr Trevor Sargent, said his thoughts were with the injured and the relatives of the dead.
"The Green Party calls on the Government to initiate a full investigation into the circumstances surrounding this horrific accident to ensure that such a tragedy does not reoccur and that transport safety is improved."
The Green Party's spokesman on transport, Mr Eamon Ryan, said Mr Brennan, should now review proposals for the introduction of a 30 km maximum speed limit in the city centre.
